The use of mistnets in forest on Yamdena (Tanimbar Islands, South Moluccas, Indonesia) revealed the presence of an undescribed bush-warbler of the genus Cettia Bonaparte, 1834. The new species is described and illustrated here and its morphological characters and vocalizations are compared with those of Asian-Pacific congeners in the subgenus Horeites Hodgson, 1845. It is considered most closely related to the Southwest Pacific warblers previously known as Vitia Ramsay, 1875. In addition, the identity of Cettia bivittata Finsch, 1901, is discussed.